1. Field of the Invention
The invention concerns a series of benzomorphan derivatives useful in the treatment of cerebrovascular disorders.
2. Background Information
Excessive excitation by neurotransmitters can cause the degeneration and death of neurons. It is believed that this excitotoxic action is mediated by the excitatory amino acids, glutamate and aspartate, acting at the N-methyl-D-aspartate (NMDA) receptor. This excitotoxic action is responsible for neuronal loss in cerebrovascular disorders such as cerebral ischemia or cerebral infarction resulting from a range of conditions such as thromboembolic or hemorrhagic stroke, cerebral vasospasm, hypoglycemia, cardiac arrest, status epilepticus, perinatal asphyxia, anoxia such as from drowning, pulmonary surgery and cerebral trauma.
The compounds of the invention, which are active as competitive antagonists of NMDA receptor-mediated ion-channel activation, are thus useful in the treatment of the above disorders. In addition, by this NMDA receptor antagonist action, the compounds of the invention are also useful for treating neurodegenerative disorders, spinal cord injury, and poisoning by exogenous NMDA poisons (for example, some forms of lathyrism). There are no specific therapies for these neurodegenerative disorders, but competitive and noncompetitive NMDA antagonists acting specifically to antagonize excitatory neurotransmission at NMDA receptors offer a novel therapeutic approach to these disorders; B. Meldrum in Neurotoxins and Their Pharmacological Implications, ed. P. Jenner, Raven Press, New York, 1987.
Recent reports in the literature have confirmed the protective action of certain NMDA antagonists in pharmacological models of neurodegenerative disorders (J. W. McDonald, F. S. Silverstein, and M. V. Johnston, Eur. J. Pharmacol., (1987) 140: 359; R. Gill, A. C. Foster and G. N. Woodruff, J. Neurosci., (1987) 7: 3343; S. M. Rothman, J. Thurston, R. E. Hauhart, G. D. Clark and J. S. Solomon, Neurosci., (1987) 21: 673; M. P. Goldberg, P. C. Pham and D. W. Choi, Neurosci. Let., (1987) 80: 11.
The present compounds have benzomorphan structures. ##STR2##
U.S. Pat. Nos. 4,108,857, 3,634,433 and 3,382,249, GB patent application No. 1185432, Japanese patent application JP A 52-3067 and Chem. Pharm. Bull. (1985, 33, 4, 1707-1710, Mikio Hori et al) disclose similar compounds as analgesic or anticonvulsant agents. J. Med. Chem. (1992, 35, 2812-2818, F. I. Carroll et al.) also disclose affinities of benzomorphan compounds for PCP, .sigma., and .mu. opioid receptors.